Process of purifying alkali metal hydroxide solutions



J1me 1936- F. OVERDICK El AL 1, 2,044,888

PROCESS OF PURIFYING ALKALI METAL HYDRQXIDE SOLUTIONS Filed D60. 26, 1934 figure according [0 example 4 iron electrode 9 i l I l H) w I 1* I raise, mfi/ f/P/n! eler/rodes figure award/ 1 [0 example 2 Vessel 4 Iran elerlrode J z, m

l I l inlet v i I 0/ the aviation L l V inallfferenl :na:4:1es

mm 1 I w 0/ Me Jo/a/ion muse! 2 ram/bade;

Patented June 23, 1936 k UNITED STATESYPATENT OFFICE PBOCES S OF PURIFYING ALKALI METAL HYDBOXIDE SOLUTIONS Fritz verdick, Level-kuaen-Wiesdorf, and Herbert i Gorke, Leverkusen-I. G. Work, Germany, assignors to I. G. Farbenindustrie Aktiengeseiicobalt, Frankfort-on-the-Main, Germany Application December 26, 1934, Serial No. 159,286

8 Claims. (01. 2049) This invention relates to a process of puriiyoi the heavy metals. Therefore, in the first con inc alkali metal hydroxidesolutlons from chlotainer cathode and anode are preferably made rate ions and heavy metal impurities, such as iron. oi iron. The efllcienoy of the anode gradually which process consists in subjecting the impure slackens, this can however be avoided by resolutions to an electrolytic treatment. versing the current from time to time, so that 5 The alkali metal hydroxide solutions obtained the cathodically connected iron sheets become by electrolysis almost in every case contain a the anode and the anodically connected ironsheets smaller or greater amount of chlorateand mebecome the cathode. tallic impurities, particularly iron, and there- Instead of the reversed continuousourrent also my iore are not suitable for many applications. an alternating current may be used in the first 10 In accordance with the present invention the stage. chlorate as well as also the heavy metal impuri- Example 2.-In a vessel containing a 50% ties are eliminated from the alirali metal hycaustic soda solution anumber of perforated iron droiride solutions Toy subjecting the solutions to sheets are-arranged parallel to one another at w electrolysis while using iron anodes. Hereby the intervals of about -30 mms. which serve as 15 iron dissolving at'the anode reduces the chlorate cathodes and anodes. The solution is heated to to chloride. The violet color first heainnina at I ahout 110? C. and a continuous current of about the anode becomes deep blue during the. treat- 10 amperes per square meter of the electrode surrocnt. than the iron present in the solution, and, face is passed through. Alter some time so much I eventualhr also other heavy metals, such as copoi the 50% caustic soda solution is introduced at so per, are eliminated from the solution by suhthe one end of the vessel that the solution runlooting the alkali metal hydroxide solution to nine ofi at the other end of the vessel is just lree cloctrolysh while using inditierent anodes, such irom chlorate. The current is reversed about richel, graphite and the like anodes. llv this evcrv t-ii hours. The solution running oil flows second treatment the heavv metals, iron, copper into a second vessel wherein a ulcer of iron to etc. are deposited upon the cathode. hath proc sheets are arranged as cathodes. Niclrel sheets can he accelerated hy applyino higher tomserve as the anodes. Through this vessel parallel eratures, say, for instance, temperatures rang I to the first vessel a continuous current oi about l irorn til-lit 3. to amperes per square ineter'oi the electrode surioventlon is further illustrated for the iollace is passed which, needless to say, must not i l lowing examples Without heina restricted there'- he reversed. to: The solution flowing on from the second vess ilcomplc i.-l;o a vessel containing 5 liters oil is practically tree from chlorate and iron. a 33% caustic soda solution a numher oi nichel We cl 1o:-

as and iron who nets are arronued parallel to one 1. Process of puiiiyinu alkali metal hydroxide 35 another and at intervals oi ahout l5 s. The solutions from chlorate and heavy metal comnichel nets connected with one another form the pounds contained therein which comprises subone', the iron nets the other electrode. e soiecting the solutions at first to an electrolytic lotion is then located to about 100 6. and a con-- treatment rvhileusing iron anodes and then to co tiuuous current is passed throuoh the solution a second electrolysis while using lndifierent whereby the iron nets serve as the anode and the anodes. nichel note as thecathode. The cm'rent density 2, proce or urifying alkali metal hydoride amou ts to bout 'h 'e i micrometer solutions from chlorate and heavy metal comoi the electrode surface. m soon as the chlorate pounds contained therein whicflcomprises is is reduced the current is reversed so that now Mating the Solutions at an elevated temperature the niclrel nets serve the anode and the iron at first to an electrolytic treatment While using nets as the cathode. The heavy metals are then mm anodes and than to a second electrolysis deposited on the iron cathode whereupon for acceleratina the process the current density is inwhile using inglfierfilt fi i an d xi 5o creased to 30 to 40 amperes per square meter of Process 0 Fur ymg hy m electrode -m solutions from chlorate and heavy metal com- The process is preferably performed, 3; anon- 'pounds contained therein which comprises subtinuous working manner, for instance, by eflect- Jecting the solutions in a first stage to an electroing in one container only the reduction or the lytio treatment while usin iron el ctrodes and chlorate, and in another container the removal reverse the poles from time to time, in a second 55 stage to-a second electrolysis while using indifferent anodes.

4. Process of purifying alkali metal hydroxide solutions from chlorate and heavy metal compounds contained therein which comprises subjecting the solutions at an elevated temperature in a first stage to an electrolytic treatment while using iron electrodes and reverse the poles from time to time, in a second stage to a. second electrolysis while using indifferent anodes.

5. Process of purifying alkali metal hydroxide solutions from chlorate and heavy metal compounds contained therein which comprises subjecting the solutions at first to an electrolytic treatment at a current density of about 10 amperes per square meter while using iron anodes and then to a second electrolysis at a current density of about 30-40 amperes per square meter while using indifferent anodes.

6. Process of purifying alkali metal hydroxide solutions from chlorate and heavy metal compounds contained therein which comprises subjecting the solutions at an elevated temperature at first to an electrolytic treatment at a current density of about 10 amperes per square meter while using iron anodes and then to a second electrolysis at a current density of about 30-40 amperes per square meter while using indiflerent anodes.

'7. Process of purifying alkali metal hydroxide solutions from chlorate and heavy metal compounds contained therein which comprises sub;- jecting the solutions in a first stage to an electroelytic treatment at a current density of about 1% amperes per square meter while using iron electrodes and reverse the pole from time to time,

in a second stage to a second electrolysis at a current density of about 30-40 amperes per square meter while using indifferent anodes.

8. Process of purifying alkali metal hydroxide solutions from chlorate and heavy metal compounds contained therein which comprises subjecting the solutions at an elevated temperature in a first stage to an electrolytic treatment at a current density of about 10 amperes per square meter while using iron electrodes and reverse the poles from time to time, in a second stage to a second electrolysis at a current density of about 30-40 amperes per square meter while using indifferent anodes.

FRITZ OVERDICK. HERBERT GORKE. 

